Chapter 3Ecosystems and Energy

Overview of Chapter 3

What is Ecology?

The Energy of Life

Laws of Thermodynamics

Photosynthesis and Cellular Respiration

Flow of Energy Through Ecosystems

Producers, Consumers & Decomposers

Ecological Pyramid

Ecosystem Productivity

Ecology

Ecology

“eco” house & “logy” study of

The study of interactions among and between organisms in their abiotic environment

Biotic - living environment

Includes all organisms

Abiotic - non living or physical environment

Includes living space, sunlight, soil, precipitation, etc.

Ecology

Ecologists are interested in the levels of life above that of organism

Ecology Definitions

Species

A group of similar organisms whose members freely interbreed

Population

A group of organisms of the same species that occupy that live in the same area at the same time

Community

Al the populations of different species that live and interact in the same area at the same time

Ecosystem

A community and its physical (abiotic) environment

Landscape

Several interacting ecosystems

Ecology

Biosphere contains earth’s communities, ecosystems and landscapes, and includes: Atmosphere -

gaseous envelope surrounding earth

Hydrosphere -earth’s supply of water

Lithosphere - soil and rock of the earth’s crust

Energy

The ability or capacity to do work

Chemical, Thermal, Mechanical, Nuclear, Electrical, and Radiant/Solar (below)

Energy

Energy exists as:

Potential energy (stored energy)

Kinetic energy (energy of motion)

Potential energy is converted to kinetic energy as arrow is released

Thermodynamics

Study of energy and its transformations

System- the object being studied

Closed System - Does not exchange energy with surroundings (rare in nature)

Open System -exchanges energy with surroundings

Laws of Thermodynamics

First Law of Thermodynamics

Energy cannot be created or destroyed; it can change from one form to another

Second Law of Thermodynamics

When energy is converted form one form to another, some of it is degraded to heat

Heat is highly entropic (disorganized)

Photosynthesis

Biological process by which energy from the sun (radiant energy) is transformed into chemical energy of sugar molecules

6 CO2 + 12 H2O + radiant energy

C6H12O6 + 6 H2O + 6 O2

Cellular Respiration

The process where the chemical energy captured in photosynthesis is released within cells of plants and animals

This energy is then used for biological work

C6H12O6 + 6 O2 + 6 H2O

6 CO2 + 12 H2O + energy

Photosynthesis and Cellular Respiration

Energy Flow

Passage of energy through an ecosystem

Producers

Primary consumers

Secondary consumers

Decomposers

Food Chains - The Path of Energy Flow

Energy from food passes from one organisms to another based on their Trophic Level

An organisms position in a food chain determined by its feeding relationships

First Trophic Level: Producers

Second Trophic Level: Primary Consumers

Third Tophic Level: Secondary Consumers

Decomposers are present at all trophic levels

Food Web

Ecological Pyramids

Graphically represent the relative energy value of each trophic level

Important feature is that large amount of energy are lost between trophic levels to heat

Three main types

Pyramid of numbers

Pyramid of biomass

Pyramid of energy

Pyramid of Numbers

Illustrates the number of organisms at each trophic level Fewer organisms

occupy each successive level

Does not indicate:

biomass of organisms at each level

amount of energy transferred between levels

Pyramid of Biomass

Illustrates the total biomass at each successive trophic level Biomass: measure

of the total amt of living material

Progressive reduction in biomass through trophic levels

Pyramid of Energy

Illustrates how much energy is present at each trophic level and how much is transferred to the next level

Most energy dissipates between trophic levels

Explains why there are so few trophic levels

Ecosystem Productivity

Gross Primary Productivity (GPP)

Total amount of energy that plants capture and assimilate in a given period of time

Net Primary Productivity (NPP)

Plant growth per unit area per time

Represents the rate at which organic material is actually incorporated into the plant tissue for growth

GPP – cellular respiration = NPP

Only NPP is available as food to organisms

Variation in NPP by Ecosystem

Human Impact on NPP

Humans represent 0.5% of land-based biomass, but use 32% of land-based NPP!

This may contribute to loss of species (extinction)

This represents a threat to planet’s ability to support both human and non-human inhabitants